The riding of bicycles over rough or mountainous terrain has grown increasingly popular over the years. The environment in which these bicycles, known as "mountain bikes," are ridden creates numerous demands on the equipment. Because the rider must propel not only his or her own weight, but also the weight of the mountain bike, a high premium is put on minimizing weight. On the other hand, due to the tremendous forces exerted on the mountain bikes during use, and the ramifications of breakage or a system failure (stranding the rider or rider injury), a high priority is placed both on durability and reliability. Furthermore, because these bikes are often ridden in undeveloped areas, it is important that almost any failure of the bike be able to be repaired by the cyclist with only the simplest of tools and a minimum of components.
For purposes of rider safety, no aspect of the mountain bike is more important than the brake assembly. In a downhill run, the brakes are applied almost continuously with varying levels of braking force. If too much brake force is applied, the rider may be thrown from the bicycle. If too little brake force is applied, the rider may lose control of the bicycle and crash. Unfortunately, due to near continuous braking in downhill situations, brake pad wear requires that brakes be adjusted often to maintain a given amount of brake handle travel for a given level of braking force.
Disc brake systems are generally recognized as having the capability of generating greater braking force than standard caliper brakes systems and various disc brake systems are available for bicycles. These systems, however, have not gained widespread acceptance. A significant problem with prior art bicycle disc brake systems is inconsistency in the requirements for generating a given kind of braking force. Specifically, in addition to the impact of brake pad wear found in standard brake systems, heat generated by braking can easily result in hydraulic fluid volume changes of 10% or more. Thus, changes in brake assembly temperatures during a single run can result in significant changes in brake handle travel for a given level of braking force. This makes the bicycle difficult to control, particularly when the cyclist pushes the envelope of his or her capabilities.
Accordingly, there is needed an improved bicycle disc brake system which is both durable, reliable, of low weight and provides for a consistent feedback for a given amount of braking force on the wheels.